fix the check for semi supervised case

[dimalvovs]

Here is a comment left by someone in the code, let's treat it properly here.

# TODO: fix this check for semisupervised case
    #  if (sum(object@featureLoadings < 0) > 0 | sum(object@loadingStdDev < 0) > 0)
     #       "negative values in feature Matrix"
      #  if (sum(object@sampleFactors < 0) > 0 | sum(object@factorStdDev < 0) > 0)
       #     "negative values in sample Matrix"